Thermal-control switch



A. J. MOTTLAU THERMAL CONTROL SWITCH Oct. 30, 1928.

2 Sheets-Sheet 1 Filed Oct. 15. 1926 INV'ENTOR Augusi' J. Mofilou ATTORNEY WITNESVSES:

Get. 30, 1928.

v A. J. MOTTLAU' THERMAL CONTROL SWITCH Filed Oct. 15. 1926 2 Sheets-Sheet 2 INVENTOR Patented Get. 30, 1928.

UNITED, STATES PATENT OFFICE.

AUGUST 3'. MOTTLAU, OF PITTSBURGH, PENNSYLVANIA, ASSIG-NOR T WESTINGHOUSE ELECTRIC 80 MANUFACT't'iIRING COMPANY, A CORPORATIONQF PENNSYLVANIA.

. THERMAL-CONTROL swircn.

My invention relates to control switches and particularly to thermally actuable con-v trol switches.

An object of my invention is to provide a thermally actuable control switch that shall be simple in construction and easily manufactured. 1

Another object of my invention is to provide a thermally actuable control switch that I shall engage and disengage, with a snap motion, contact members associated therewith.

Another object of my invention is to provide a thermally actuable control switch that shall have a small difierential of temperature between the engaged and disengaged positions of its contact members.

Another object of my invention is to provide a thermally actuable control switch that may be easily adjusted for operation over a relatively wide range of temperatures.

A further object of myvinvention is to pro vide a thermally actuable control switch that may be manufactured from a single sheet of material by a simple stamping operation.

In practicing my invention, I provide a resilient metallic frame in which a pair of elongated apertures are so punched that a bridging member remains therebetween. The sides of the frame are provided with deformed portions, thereby causing the bridging member to be substantially longer than the apertures. The bridging member is provided with deformed end portions that extend laterally of the plane of the frame.

A contact member is so mounted on the bridging member that it cooperates with a stationary contact member which is adjustably mountedon a. support for the frame member. A deflection of the ends of the frame in a direction substantially perpendicular to the plane of the frame is sufiicientto cause'the bridging member to deflect with a snap motion in a direction opposite to the deflection of the end portions, thereby causing the contact members to be disengaged positively and at a high rate of speed.

V In the drawings,

Fig. 1 is a top plan view of a device embodying my invention,

Fig. 2 is a view, in vertical section, taken on the line 11-11 of Fig. 1,

Fig. 3 is a view, in vertical section, of the device illustrated in Fig. 1, taken on the line file-III thereof,

Fig. 4 is a view, in longitudinal vertical section, of the device illustrated inFig. 2 in its inoperative position,

Fig. 5 is a top plan view of a modified form of the'device illustrated in Fig. 1,

Fig. 6 is'a view, in vertical section, taken on the line VIVI of Fig. 5,

Fig. 7 is an end view of the device illustrated in Fig. 5, and

Fig. 8 is a view, similar to Fig. 6, illustrating the device of Fig. 6 in an adjusted position.

Referring; more particularly to Figs. 1 to 4. of the drawings, a thermally-actuable switch 11 comprises a supporting and insulati member 12 and a switch member 13. Theaswitch member 13 comprises a metal frame 14; that has an aperture 15 therein and a bridging member 16 which extends thereacross and is either secured tothe frame or is integral therewith. The bridging member 16 is preferably made integral with the frame 14 by punching out certain longitudinally-extending portions of metal to form a pair of spaced relatively narrow apertures 17 and 18 at each side of the bridging member 16.

The longitudinally-extending sides of the frame 14. have deformed portions 19 of substantially W-shape located preferably at the middle thereof. The bridgingmember 16 has curved end portions 21' and 22.. (See Fig. 2.) The dimensions of the deformed portions 19 .arefsuch as to makethe bridging -member 16 substantially longer than the straight-line distance between points 23 and 24 and also to make the middle portion of the member 16 assume an arched position.

The arching of the member 16 is of such degree as will. bias a contact member 25 mounted thereon into engagement with a stationary cont-act member 27 mounted on the frame member 12. The position of the points 23 and 24, with respect to the contact member 27, may be varied by increasing or decreasing the pressure of a pair of screwthreaded members 28 and 29, which extend through the deformed portions 19 of the frame 14 and the supporting member 12.

If the control switch illustrated in Figs. 1 to 4, inclusive, is made from bimetallic material, it is self-actuated when subjected to predetermined temperatures.

When the frame 14 is made of a bimetallic material and is shaped substantially as illustrated in the drawings and so disposed on the base 12 and secured thereto that the metals thereof having the high and the low thermal coefiicients of expansion are repre sented by the surfaces 31 and 32 respectively, the frame, when subjected to a predetermined temperature, will assume a curved position (see Fig: 4). If the frame 14 has been actuated to this position, the contact member 25 will have been pressed against. the contact member 27 until a portion of the bridging member 16 between the'deformed portions 21 and 22 has been deflected to a state of unstable equilibrium, from which state thesaid portion reverses its curvature with a snap motion. The bridging member 16 will then have been deflected to the position illustrated in Fig. 4, and the contact member 25 will have been disengaged from the contact member 27. with a snap motion.

The temperature at which the switch 11 is operable to disengagethe contact members 25 and 27 is dependent upon the pressure of the screw members 28 and 29 upon the deformed portions 19 and also upon the pressure exerted by the contact member 27 upon the contact member 25. The latter pressure may be adjusted by means of a screw-threaded member 33 on which the contact member 27 is mounted. It is to be understood that the member 33 may be made of such length, that, when turned in the prop er direction, it will cause the central portion of the bridging member 16 to be deflected upwardlya predetermined amount.

The screw-bolt member 28, which serves to hold one side of the frame 14 in en agement with the supporting member 12, unctions as one terminal of the switch 11. The screw-bolt 29 serves to maintainthe other side of the frame 14 in engagement with the supporting frame 12 and' also as an adjusting means. for the switch 11. The screwbolt 33, which also maintains the contact member 27 in a stationary position on .the

. supporting frame 12, serves as a second terminal for, the switch 11.

The frame 14 has a pair of depending end portions 34 and -35 which may be caused to register with a suitableactuating member, in the event that it is desired to make the switch 11 of non-bimetallic material, such as a thcr mo-responsive device.

In Figs. 5 to 8, inclusive, 1' have illustrated a modification of the switch illustrated in Figs. 1 to 4. In this modification, a control switch 11a comprises a frame 14a such as is hereinbefore described but made of a single metal and a thermo-responsive actuating member 36.

The member 14a, illustrated more clearly in Figs. 6 and 8, is provided with a pair of laterally extending deformed portions 40 and 41 in the two side portions thereof and the bridging member 16a is provided with a pair of curved end portions 42 and 43.

The frame member 36 comprises a bimetallic plate that is provided with a single elongated, irregular aperture 39 and depending end portions 37 and 38 that engage the depending end portions 34 and 35 of the member 14a.

Each side of the frame 36 is provided with a pair of deformed portions 44 of substantially W-shape that are preferably disposed -member 36 in operative engagement. with the member 14a so that the end portions 37 and 38 are in engagement with the end portions 34 and 35 or in close proximity thereto.

The member 36 is preferably made of bimetallic material, but the member 14a may be made either of a bimetallic or a non'bimetallic material, as desired. An increase in the temperature of the bimetallic member 36 will cause the end portions 37 and 38 to press against the end portions 34 and 35 until the bridging member 16a is deflected to a state of.unstable equilibrium. Upon a further increase of temperature, the bridging member 16a suddenly changes its curvature to cause the contact members 25 and 27 to be disengaged with a snap motion. Each of the members'14a and 36 'is secured to the supporting and insulating base 12.

In Fig. 8 of the drawings, I have illustrated the deformed portion 44 as having been widened or increased in length by increasing the pressure of the bolts 28 and 29 thereon. By so doing, the end portions 37 and 38 are moved away from the end portions 34 and 35 so that a time delay is attained, when subjecting the switch member 11a to a temperature to be controlled, before the end portions 37 and 38 can actuate the contact members 25 and 27 ut of engagement;

f it is desired that the control switch illustrated in Figs. 1 to 4, inclusive, and its modification illustrated in Figs. 5 to 8, in-

' contact members 25 and 27 at" a relatively high temperature, it is necessary that the screw-bolts 28 and 29 shall pr'esswith a relatively small force on the deformed portions 19, illustrated in Figs. 1 to 4, and the deformed portions 44, illustrated in Figs. 5 to 8.

If it is desired that the switch shall be operable at a relatively low temperature, the

bolts 28 and 29 must press with suflicient force on the deformed portions 19 and 44 to produce such initial stress on the bridging member 16 that a relatively small expansion-hence a relatively low temperature of the binietallic actuating member 36is necessary to actuate the bridging member 16 to a position at which the contact members 25 and 27 shall be out of engagement with one another.

When the device illustrated in the drawings is made of a bimetallic material and is to be applied to devices for controlling temperatures comparable with those common to refrigeration, the bimetal should be reversed from the showings in Figs. 1 to 8, inclusive, so that the surface 31 represents the low-expansion side and surface 32'represents the high-expansion side.

The device embodying my invention has many applications for controlling the temperature of such devices, as electric transformers, electrically-heated flat irons, refrigerators'and the like.

Various modifications may be made in the device embodying my invention without de parting from the spirit and the scope thereof. I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. A thermally-actuable switch comprising a resilient frame having an elongated aperture therein, a bridging member secured to said frame and extending across said aperture and means cooperating with a deformed portion of said frame for applying an initial longitudinal stress to said bridging member.

2. A thermally-actuable switch comp-rising a resilient bimetallic frame having an elongated aperture therein, a bridging member secured to said frame and extending across said aperture and means cooperating with a deformed portion of said frame for applying an initial longitudinal stress to said bridging member. V

3. A thermally-actuable switch comprising a resilient bridging member disposed between a pair of supports and restrained against lon-I gitudinal movement, said bridging member being substantially longer than the distance between said supports, and a bimetallic frame member having up-turned end portions in engagement with sald supports for actuating member operatively said bridging member laterally with a snap motion.

4. A thermally-actuable switch comprising a resilient bridging member disposed between a pair of supports and restrained against longitudinal movement, said bridging member being substantially longer than the distance between said supports, a bimetallic frame member having upturned end portions in engagement with said supports for actuating said bridging member laterally with a snap motion, and means integral with'said bimetallic member for Varyingthe initial position of the upturned end portions thereof,

with respect to the ends of said bridging member.

5. A thermally-actuable switch comprising a resilient bridging member disposed between a pair of supports and restrained against longitudinal movement, said bridging member being substantially longer than the distance between said supports, a bimetallic frame member having upturned end por tions in engagement with said supports for actuating said bridging member laterally with a snap motion, said'bimetallic frame member having a deformed portion of sub stantially W-shape, and means for changing the proportions of said deformed portion in. accordance with a predetermined thermal condition at which said bimetallic member shall be operable to actuate said bridging member.

6. An electric switch comprising a resilient frame member having an aperture therein, said frame having deformed portions at the sides of said aperture extending laterally of the plane thereof, means for controlling the amount of deformation of said deformed portions, and a resilient bridging member of substantially greater length than said aperture extending thereacross in operative relation with said frame member.

7. An electric switch comprising a thermoresponsive bimetallic frame member having an aperture therein, said frame havingdeformed portions at the sides of said aperture extending laterally of the plane thereof, means for controlling the amount of deformation of said deformed portions and a resilient bridging member of substantially greater length than said aperture extending thereacross in operative relation with said frame member.

8. An electric switch comprising an elongated resilient member for controlling a con.- tact member, said member having end .portions deformed laterally of the plane thereof and being restrained from longitudinal movement, a thermo-responsive bimetallic frame engaged to the ends of said elongated member for actuating a portion thereof laterally with a snap motion in response to a. predetermined temperature mediate its thereof, and means for changing'the length and position of said frame relatively to said bridging member for controlling the temperature at which said frame shall be operable 6 to actuate said elongated member.

9. A thermally-actuable electric switch comprising a support, a stationary cont-act member mounted thereon, a resilient apertured frame having a. portion thereof interends secured tosaid support, a bridgin member of substantially greater length t Ian the aperture of said frame member extending thereacross in operative engagement' therewith, said bridging member being biased to normally maintain a movable contact member associated therewith in engagement with the stationary contact member, and means for changing the initial curvature of said frame member to produce a pre determined initial stress on said bridging member.

In testimony whereof, I have hereunto subscribed my name this llth day of October, 1926.

AUGUST J. MOTTLA'U. 

